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Thursday, June 2, 2011

Pacific lamprey, Lampetra tridentata, are very primitive, eel-like fish that historically were widely distributed from Mexico north along the Pacific Rim to Japan. They are culturally important to indigenous people throughout their range, and play a vital role in the ecosystem as food for mammals, fish and birds, for nutrient cycling and storage, and as a prey buffer for other species. Lamprey are also used for scientific research, educational purposes, vitamin oil, and anti-coagulants.

Pacific lamprey spawning

(Photo: K. Figlar-Barnes, WDFW)

Pacific lamprey are anadromous, meaning that they live in both fresh and salt water. Adults are parasitic and live in the ocean where they feed on the blood and bodily fluids of marine mammals and fish. After about 2 years in the ocean, they return to fresh water streams to spawn. After entering fresh water, the adults either stop feeding and spawn or they overwinter and spawn the following spring. Lamprey construct nests (redds) in small gravel where they lay their eggs. Like salmon, lamprey die soon after spawning. Eggs hatch after several weeks and the blind larvae are called ammocoetes. The ammocoetes live in fine sediment, filter feeding on algae and detritus. After 4 to 6 years as an ammocoete, Pacific lamprey metamorphose to a juvenile life stage called macropthalmia. The juvenile lamprey migrate out to the ocean where they mature into adults, growing to about 2 feet in length.

Pacific lamprey are vulnerable to many of the same threats that have reduced salmon populations. These threats include poor habitat conditions, water pollution, and dam passage. Like salmon, the abundance and range of Pacific lamprey have been reduced. To improve their distribution and abundance, we are working with our partners to address threats, restore habitat, and fill in large data gaps on Pacific lamprey. One of the data gaps we are currently addressing is the distribution and abundance of spawning lamprey in Washington coastal rivers in the Chehalis and Willapa River basins.

Beginning in March and continuing through June, Washington Department of Fish and Wildlife (WDFW) biologists and scientific technicians conduct spawning ground surveys to estimate natural spawning steelhead populations. The survey crews identify and monitor steelhead redds and, since 2005, have also been counting any Pacific lamprey redds and adults they see during these surveys. Because some of the steelhead index survey coverage does not include the Pacific lamprey spawning timing, we contracted with WDFW in 2010 to cover the lamprey spawning period from June through August.

For this project, WDFW selected 30 (50%) of their 60 steelhead index reaches to survey for lamprey. Indexes were selected based on previous years’ lamprey spawning timing, redd density, habitat type, location within the basin, and proximity to other indexes. Similar to the steelhead program, surveys were conducted every 10 to 14 days and began on June 1. Survey staff were instructed to record all visible Pacific lamprey redds along with any live or dead adults they saw. This visible redd count data provides relative abundance estimates and spawning timing data.

Mid to late July appears to be the end of the spawning time period for Pacific lamprey in both the Willapa and Chehalis basins; 28% of the visible lamprey redd activity occurred after the WDFW cut-off date used for steelhead spawning ground surveys. A total of 539 redds were observed in 2010---this is very encouraging as it is an increase compared to the previous 2009 spawning season (see graph below). However, the 2010 redd count data was down by an estimated 37% compared to the average number of redds over the 2005-2009 spawning seasons.

As funding allows, we hope to continue these extended Pacific lamprey redd surveys in the future so that we can use this data to monitor the status of these fish populations.

About Us . . .

We are an integrated team of experienced fish and wildlife biologists, hatchery operation specialists, bio-statisticians, and support personnel. As a result of our diverse technical expertise, we are able to explore a variety of factors affecting wild and hatchery fish and other aquatic resources. Our team is dedicated to the recovery and maintenance of our trust resources.